Computer simulation of fluorescence spectra for molecular ring: exciton dynamics

Software package Mathematica is used for computer simulation of steady state fluorescence spectra of ring molecular system. The cyclic antenna unit LH2 of the bacterial photosystem from purple bacterium Rhodopseudomonas acidophila can be modeled by such system. Dynamic disorder, interaction with a bath, is included in Markovian approximation. Also three different models of uncorrelated static disorder are taking into account in our simulations: Gaussian disorder in local excitation energies, Gaussian disorder in nearest neighbour transfer integrals and Gaussian disorder in radial positions of molecules in the ring. The cumulant-expansion method of Mukamel et al. is used for the calculation of spectral responses of the system with exciton-phonon coupling. The peak positions of single ring spectra and localizations of exciton states depend on realization of static disorder. Dynamic disorder also influences the peak position. We discuss different types of exciton dynamics, that are coupled to above mentioned effects. Key–Words: LH2; fluorescence spectrum, static and dynamic disorder, exciton states and dynamics, Mathematica